Our laboratory and others are attempting to map the "engram" or the memory trace throughout the brain, and we have been successful in identifying brain regions that are important for the acquistion of trace eyeblink conditioning, such as the hippocampus and several cortical regions. This study will investigate a role for the basal ganglia in the acquistion and consolidation of trace eyeblink conditioning. To achieve this, this study will take recordings from, permanently lesion, temporally inactive, and neurochemically deplete the caudate nucleus, a major site of cortical and thalamic input into the basal ganglia. In Specific Aim 1, electrodes will be lowered into the caudate nucleus and single unit recordings will be made in the awake, behaving, and learning rabbit for 14 days as the animal acquires and stores this memory. This experiment will reveal whether learning related changes in neuronal activity occur in the caudate nucleus during learning. In Specific Aim 2, the caudate nucleus will be electrolytically lesioned before and after training to determine if it is necessary for the acquistion or retention of this memory, respectively. The findings from these experiments will guide a third study in which muscimol will be infused into the caudate nucleus in order to determine whether the basal ganglia is essential for the expression or learning of trace eyeblink conditioning. In Specific Aim 3, 6-OHDA will be infused into the caudate nucleus in order to eliminate dopamine, which is thought to provide a teaching signal in the basal ganglia network. This experiment will begin our investigation into the neurochemistry of the basal ganglia that might underlie learning and memory. Taken together, these findings will advance our understanding of how memory is acquired and stored in neural networks. With a fuller understanding of how memory is manifested in the brain, we can identify novel therapeutic targets for treatment of dementia and learning disabilities. This project attempts to identify bain regions that are responsible for the acquisition and consolidation of memory and decribe precisely how these brain regions participate in memory formation and storage.